It is frequently desirable to provide a secure content delivery mechanism for transferring protectable subject matter from one node to another. One example of such a mechanism is the provision of digital video and/or audio over a Digital Video Interface (DVI) or High-Definition Multimedia Interface (HDMI). DVI and HDMI often use a mechanism called High-bandwidth Digital Content Protection (HDCP) to prevent the interception of the audio/video between the content source and destination. By using HDCP, data, such as copyright protectable movies and music, can be securely transmitted with a reduced likelihood of theft.
HDCP is required, by standard, to be delivered over a physical link, such as an HDMI cable. Furthermore, connections between two such links require the use of a repeater that provides endpoint data encryption termination to both links, and fulfills any encryption and/or key requirements for each individual link. HDCP repeaters are generally described in the document “High-bandwidth Digital Content Protection System,” Revision 1.1, Jun. 9, 2003, (hereinafter “HDCP System Standard”) which is hereby incorporated by reference into the present application in its entirety.
HDCP compliant devices are required, by standard, to have a unique key set (“DKS”), including 40 56-bit secret device keys, referred to as Device Private Keys, and a 40-bit identifier, referred to as the Key Selection Vector (“KSV”). During authentication, a transmitter (“Device A”) sends to a receiver (“Device B”) a message containing the transmitter's KSV (“Aksv”) and a 64-bit pseudorandom value An. Device B responds with the receiver's KSV (“Bksv”) and indicates whether Device B is a repeater. Device A verifies that Bksv has not been revoked and that it contains 20 ones and 20 zeros. Both devices then generate a session key (“Ks”), which is a 56-bit secret key for the HDCP cipher, a 64-bit secret value (“Mo”) that is used for the next phase of authentication, and a 16-bit response value (“Ro”) to indicate success of the authentication exchange.
If Device B is a repeater, the device gathers a list of downstream KSVs to report upstream. The KSVs are checked upstream to determine whether they have been revoked. The final step in authentication occurs during the vertical blanking period and involves both of the devices calculating new cipher initialization values Ki, Mi, and Ri, wherein the index i represents the frame number staring with 1 for the first video frame that is encrypted.
A general trend towards wireless links exists. However, as stated above, some transmission mechanisms, such as HDCP, cannot be provided over a wireless link. Therefore, a need exists to provide a wireless link between two nodes in which transmission mechanisms like HDCP would otherwise be provided.